使用golang向DynamoDB封送/解组“枚举”

时间:2019-07-11 15:15:24

标签: go enums amazon-dynamodb marshalling

我在go中拥有以下PartnerType“枚举”结构:

// PartnerType enum
type PartnerType int

const (
    // PartnerTypeUnknown should never happen
    PartnerTypeUnknown PartnerType = iota

    // PartnerTypeTest test
    PartnerTypeTest
)

func (t PartnerType) String() string {
    names := [...]string{
        "UNKNOWN",
        "TEST"}

    if t < PartnerTypeUnknown || t > PartnerTypeTest {
        return names[0]
    }
    return names[t]
}

// MarshalJSON for enum
func (t PartnerType) MarshalJSON() ([]byte, error) {
    s := t.String()
    return json.Marshal(s)
}

// UnmarshalJSON for enum
func (t *PartnerType) UnmarshalJSON(b []byte) error {
    *t = PartnerTypeUnknown
    return nil
}

// MarshalText implements the text marshaller method
func (t *PartnerType) MarshalText() ([]byte, error) {
    return []byte(t.String()), nil
}

// UnmarshalText implements the text unmarshaller method
func (t *PartnerType) UnmarshalText(text []byte) error {
    *t = PartnerTypeUnknown
    return nil
}

// Partner entity
type Partner struct {
    ID   string `dynamodbav:"PK,omitempty"`
    Foo string `dynamodbav:"SK,omitempty"`
    PartnerType              PartnerType    `dynamodbav:",omitempty,string"`
}

执行dynamodbattribute.MarshalMap()时,我希望将PartnerType存储为字符串。 dynamodbav struct标记允许您将int作为字符串(dynamodbav:",omitempty,string")存储,但是它没有调用我定义的.String()Marshal/Unmarshal实现。

用另一种方式表示,它将PartnerTypeTest存储为"1"而不是"TEST"

这怎么办?

1 个答案:

答案 0 :(得分:1)

对于dynamodb,您可以为枚举实现marshaler / unmarshaler

尝试以下操作:

// MarshalDynamoDBAttributeValue for ddb
func (t PartnerType) MarshalDynamoDBAttributeValue(av *dynamodb.AttributeValue) error {
    s := t.String()
    av.S = &s
    return nil
}

// UnmarshalDynamoDBAttributeValue implements the Unmarshaler interface
func (t *PartnerType) UnmarshalDynamoDBAttributeValue(av *dynamodb.AttributeValue) error {
    // val := aws.StringValue(av.S)

    *t = PartnerTypeUnknown
    return nil
}